Mass shootings in Western states, by the numbers

In October, a man opened fire at Umpqua Community College in Oregon, leaving 10 dead.

Editor's note: This map and database in this article have been updated with details on a shooting at a Planned Parenthood in Colorado Springs, Colorado and a subsequent shooting in San Bernadino, California. This story had been updated with the latest news available.

On Thursday, Oct. 1, a man identified as at Umpqua Community College, in Roseburg, Oregon. By the time his rampage was done, he had killed 10 people, including himself, and left several more injured. As is common in the wake of mass shootings, details about the incident will be slow to emerge and the facts of what happened will likely remain somewhat murky.

These types of public mass shooting incidents and Western states have been the site of some of the most high-profile events, from to the Aurora theater shooting in 2012and the Oregon mall shooting three years ago. Many of these shooters had been diagnosed with mental illness — as were almost one in every five American adults overall, according to a

Two women pray by candles spelling out the initials for Umpqua Community College after a candlelight vigil Thursday, Oct. 1, 2015, in Roseburg, Ore. A man opened fire at the school before dying in a shootout with police.

John Locher/AP

The factors that feed the rampages are a matter of dispute and the landscape of gun ownership and regulation out West is complicated. On the one hand, the myth of the West's gun-rife past has been exaggerated. As a region, the West actually has the second lowest rate of gun ownership in the country, according to . Just over a third of Westerners own at least one gun, compared with 35 percent of Midwesterners and 38 percent of Southerners. But that number covers a large range; both some of the highest and lowest gun-owning states are Western. According to a study published earlier this year in the peer-reviewed journal Injury Prevention, just 20 percent of households in California have a gun. But in Wyoming, Alaska, Idaho and Montana, more than half do.

The region also is home to some of the nation's weakest gun laws, according to reporting from the . Alaska, Arizona and Wyoming place virtually no restrictions on concealed or open carry and many others do only slightly more, requiring easy-to-obtain permits. Efforts to tighten regulations have been met with severe backlash in some states. In Colorado, several lawmakers who voted in favor of bills that required universal background checks for handgun sales and banned high capacity magazines lost their seats in the years that followed.

In light of October's horrific event, here is a look at mass shootings and killings in Western states, by the numbers:

1. Where do mass killings happen? This map, made using , includes only incidents in the U.S. where four or more people were murdered, since 1982. Explore the map by zooming in and out or by searching for a location. Learn more about each incident by clicking on the red dots.

Note: A yellow dot indicates a developing incident.

2. Couldn't find a recent incident? Try this database of mass shootings from , which covers 2015. Search by shooter name, date, city or state. It includes mass killings, but also shooting incidents where fewer than four people died. The database also includes media coverage of each incident. This will be updated as incidents develop.

Kate Schimel is a correspondent for NewTowncarShare News and is based in Seattle.